Influência da incorporação de negro de fumo e carbonato de cálcio micro e nanoparticulado nas propriedades reológicas, colorimétricas e mecânicas de filmes de polietileno de baixa densidade

Abstract

In this work, the influence of incorporation of Carbon Black (CB) and CaCO3, both with different particle sizes, on the rheological, colorimetric and mechanical properties of LDPE films were studied. Three different types of CB were selected, with particle sizes of 15, 38 and 75 nm and combined together, generating a DOE with 19 combinations dispersed in LDPE by twin screw extrusion. Such formulations were evaluated in function of performance and processability properties, such as Tint Strength, Filter Pressure Value (FPV) , Melt Flow Index (MFI) and Viscosity. It was determined that the best formulation was a combination between small (P) and medium (M) particles, obtaining the highest tinting and lowest viscosity. Thus, it was studied by varying the process, depending on the speed of the screw (N) and feed rate (Q), to modulate the Specific Mechanical Energy (SME) which, can contribute to better dispersion of pigments. Finally, once formulation and process had been defined (600 rpm and 10 kg/h), CaCO3 was added, micro (D50 = 2.5 μm) and nanoparticulate (D50 = 40 nm) sizes at 10% and 20%, aiming to improve the economic aspect and gain in mechanical properties, maintaining the tinting strength, total transmittance, FPV and viscosity already obtained, however CaCO3 has a high refractive index and acted as low-performance white pigment, decreasing the tinting and increasing the FPV, in addition to interfering in the viscosity. Changes in these properties were observed, however, to a lesser extent with nanoparticulate filled at 10% (F18-P03-N10). The best balance of properties is directly associated with the final application of the formulation such as extrusion or injection molding that require specific characteristics of the concentrate.